Method of operating open-hearth furnaces



y 1951 K. H. MOODY 2,550,848

METHOD OF OPERATING OPEN-HEARTH FURNACES Filed March 16, 1948 2Sheets-Sheet 2 lawenlar: A f/fi/ M000),

Patented May 1, 1951 METHOD OF OPERATING OPEN-HEARTH FURNACES Keith H.Moody,.Duluth, Minn, assignor to The American Steel & Wire Company ofNew Jersey, a. corporation of New Jersey Application March 16, 1948,Serial No. 15,233

6 Claims.

This invention relates to a method of operating open hearth furnaces andmore particularly to operating such furnaces when they are using scrapmetal as part of the charge. In the operation of such furnaces, scrap isfirst charged into the furnace and melted down, after which cold and/orhot iron are added and the entire charge refined. Various types offuel,-such as gas, oil

a and tar, are used in heating the furnace. In

some instances a combination of gas and oil or tar is used. Thisinvention relates to those furnaces in which oil or tar are usedseparately or in combination with gas and for the purpose of thisapplication, any fuel made up in whole or in part of a liquid will betermed liquid fuel. In heating the charge, the heat is suppliedalternately from each end of the furnace and ordinarily a single burneris used at each end of the furnace.

Due to normal furnace construction and the relative position of thebridge walls and burners, it has been difficult to provide the air in amanner to obtain combustion of the liquid fuel close to the entrance endof the furnace when using a single burner at top capacity. As a result,a considerable amount of fuel burns near the exit end of the bath or mayeven burn as it leaves the furnace through the downtakes. We have foundthat by introducing compressed oxygenfdirectly below the fuel stream thespeed of combustion is increased with an accompanying increase inmelting rate and fuel efiiciency. It has been suggested that oxygen beintroduced around the periphery of the fuel outlet, but'this does notact in a satisfactory manner and tends to burn the roof. When oxygen issupplied in the manner of my invention it has been found that the rooftemperature will be lower than normal.

I t It is an object of this invention to provide a method of firing anopen hearth furnace in which oxygen is introduced into the furnacedirectly beneath the fuel stream.

Another object is to provide a burner especially adapted for carryingout my method.

These and other objects will be more apparent after referring to thefollowing specification and attached drawings, in which:

Figure 1 is a plan view, partly in section, of one-half of an openhearth furnace showing my burner in place;

Figure 2 is a longitudinal section of the furnace of Figure 1 takenthrough the front uptake;

Figure 3 is a longitudinal elevation of the burner of my invention;

Figure 4 is an enlarged longitudinal section of the burner of Figure 3;

Figure 5 is a sectional view taken on the line V-V of Figure 4; and

Figure 6 is a sectional View taken on the line VIVI of Figure 4.

Referring more particularly to the drawings, the reference numeral 2indicates the hearth of an open hearth furnace. The furnace issubstantially symmetrical about its transverse center line and thereforeonly one-half thereof is shown in the drawings and will be describedherein. A burner tunnel t is provided through the end wall 6 anda-liquid fuel burner 8 is arranged approximately on the center line ofthe furnace with its axis arranged at. an angle to intersect the'surfaceof the charge.

As shown in Figures 3 to 6, the burner 8 consists of a casing it insideof which near the top thereof is a conventional oil burner l2 made up ofthree concentric pipes l4, l6 and i8. Steam is supplied through theinner pipe l4 and oil is supplied through the pipe I6 around the pipe M.The oil passes through holes 29 in pipe I 4 at the nozzle 22 where itmixes with the steam in the usual manner. An air space is providedbetween the pipes l6 and I8. Beneath the oil burner I2 is a longitudinalpipe 24 which contains an oxygen supply pipe 26. The end of the pipe 26extends beyond the end of the burner a distance of between one andtwelve inches, preferably between six and twelve inches. rounds thefront part of the pipe 26 and water is supplied thereto through a pipe39 with the water exhausting therefrom through a pipe 32. Water issupplied to the casing l0 through pipes 34 and exhausts through a pipe36. The usual valves are provided for regulating the flow of the variousfluids.

The burner 8 may be located on the exact center line of the furnace orits axis may be tilted a slight amount toward the front of the furnaceas shown. For example, it might be aimed at a point three feet from thelongitudinal center line on the opposite end wall of the furnace. Thevertical angle of the burner is preferably such that the flame strikesthe top of the bath 38-at a point in line with the center line of thefirst furnace door 40. In addition to the door 68, the front wall 42 isprovided with doors 44 and 46, the door 46 being on the center line ofthe furnace and two doors similar to doors a0 and 44 being located onthe opposite side of the center line. The furnace is provided with theusual back wall 48. Air for combustion is supplied from the checkerchamber 50 through air uptakes 52 and flows into the melting chamber 54around the stream of fuel from burner 8. The mixing of the fuel and airis accelerated as it passes through the restricted passageway or throat56.

The furnace is operated as follows:

-Metal scrap is charged into the furnace, the burner I2 is started inoperation and oxygen is introduced through the pipe 26. The air from thechecker chamber 50 flows upwardly through the uptake 52 around thestreams of fuel flow- A pipe 28 suring from the burner. The velocity ofthe oxygen stream is preferably approximately the same as the velocityor" the flame but may vary from onesixth to two times the velocity ofthe flame, this being sufficient to enable the oxygen to penetrate thecone of the fuel stream flame at a point approximately 2 feet from theend of the fuel jet. By supplying oxygen in this manner the greatestamount of heat is directed downwardly on the charge where it is mostuseful. The oxygen is preferably turned off at the end of the melt-downperiod or at least a short time after the lime boil, but ma if desiredbe used to raise the temperature of the molten bath after additions havebeen introduced while working the heat. It will be understood that thefurnace will otherwise be operated in the usual manner. That is, it willbe reversed at intervals and on each reversal, the burner and oxygenwill be shut off at one end and the burner and oxygen at the other endwill be turned on.

While one embodiment of my invention has been shown and described, itwill be apparent that other adaptations and modifications may be madewithout departing, from the scope of" the following claims.

I claim:

1. In the method of making steel in the melting chamber of an openhearth furnace which includes the steps of charging metal scrap into thefurnace, the improvement in the melting step thereof comprisingprojecting a stream of liquid fuel from a burner into one end of andlongitudinally of said chamber, said stream being directed downwardly atan angle to impinge on said charge, flowing into said chamber a streamof preheated air around said stream of fuel, and introducing a stream ofoxygen into said chamber only directly below and in the samelongitudinal vertical plane as the fuel, said stream of oxygen enteringsaid chamber ata point between one and twelve inches from the furnaceend of the burner.

2. The method of making steel in the melting chamber of an open hearthfurnace according to claim 1 in which the velocity of the oxygen at thepoint of introduction is approximately the same as the velocity of thefuel.

3. The method of making steel in the melting chamber of an open hearthfurnace according to claim 1 in which the oxygen is shut off after thescrap is well melted down.

4. The method of making steel in the melting chamber of an open hearthfurnace according to claim 2 in which the oxygen is shut off after thescrap is well melted down.

5. In the method of making steel in the melting chamber of an openhearth furnace which includes the steps of introducing a metal chargeinto the furnace, the improvement in the melting step thereof comprisingprojecting a stream of liquid fuel from a burner into one end of andlongitudinally of said chamber, said stream being directed downwardly atan angle to impinge on said charge, flowing into said chamber a s.rean1of preheated air around said stream of fuel, and introducing a stream ofoxygen into said chamber only directly below and in the samelongitudinal Vertical plane as the fuel, said stream of oxygen enteringsaid chamber at a point between one and twelve inches from the furnaceend of the burner.

6. The method of melting metal in the melting chamber of an open hearthfurnace which includes the steps of charging metal scrap into thefurnace, projecting a stream of liquid fuel from a burner into one endof and longitudinally of said chamber, said stream being directeddownwardly at an angle to impinge on said charge, flowing into saidchamber a stream of preheated air around said stream of fuel, andintroducing a stream of oxygen into said chamber only directly below andin substantially the same longitudinal vertica1 plane as the fuel, saidstream of oxygen entering said chamber at a point between one and twelveinches from the furnace end of the burner.

KEITH H. MOODY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,659,869 Gow Feb. 21, 19281,712,326 Brock May 7, 1929 1,718,732 Danforth, Jr June 25, 19291,830,574 Thwing Nov. 3, 1931 1,917,031 Hamilton July 4, 1933 1,955,589Leahy Apr. 17, 1934 2,243,987 Stokes June 3, 1941 2,362,085 Morgan Nov.7, 1944 2,417,951 Schwartz Mar. 25, 1947 2,446,511 Kerry et a1 Aug. 3,1948 OTHER REFERENCES A. I. M. E. Open Hearth Proceedings, pages 68, 69,73, 74, 76, and 82. Published in 1947 by the A. I. M. E., New York, N.Y.

The Foundry, October 1947, pages 74, and 76. Published by th PentonPublishing Co., Cleveland, Ohio.

1. IN THE METHOD OF MAKING STEEL IN THE MELTING CHAMBER OF AN OPENHEARTH FURNACE WHICH INCLUDES THE STEPS OF CHARGING METAL SCRAP INTO THEFURNACE, THE IMPROVEMENT IN THE MELTING STEP THEREOF COMPRISINGPROJECTING A STREAM OF LIQUID FUEL FROM A BURNER INTO ONE END OF ANDLONGITUDINALLY OF SAID CHAMBER, SAID STREAM BEING DIRECTED DOWNWARDLY ATAN ANGLE TO IMPINGE ON SAID CHARGE, FLOWING INTO SAID CHAMBER A STREAMOF PREHEATED AIR AROUND SAID STREAM OF FUEL, AND INTRODUCING A STREAM OFOXYGEN INTO SAID CHAMBER ONLY DIRECTLY BELOW AND IN THE SAME LONGITU-